The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia.
Belt and auger conveyors are not constraining of the material and/or have a high maintenance requirement. Impeller pumps of are less than suitable due to the impeller coming into contact with the abrasive mixtures.
Pneumatically operated pumps for entrained particulate materials find increasing use, particularly in offshore and terrestrial drilling applications. The technology provides large throughputs with pumps of a minimum number of moving parts, and which can be hardened or provided with cheap sacrificial parts to accommodate, hot, corrosive and/or highly erosive material flows. The use of pneumatic power may substantially remove electrical componentry from an aggressive environment.
WO/2006/037186 describes pump apparatus including a housing having a material inlet for a material to be pumped and a delivery outlet, a valve on each of the inlet and outlet, and control means for selectively opening and closing the respective valves and cycle the pressure in the housing. When the pressure is low in the housing while the inlet valve is open, material is admitted to housing. When the control means effects closure of the inlet valve, the housing is pressurized and the outlet valve is open to discharge said material from said housing. The pressure cycling is achieved with compressed air and a venturi. This apparatus can be entirely pneumatic in operation, avoiding reliance on electronics for its fundamental operation.
In order to scale throughput, multiples of the units may be used. However, the unit is of a certain irreducible size dictated by the volume of the pot forming the working chamber for the ejector/pressure system to work on.
PCT/AU2007/001107 describes a scalable-output development of the above described pump wherein four pots are associated with an inlet manifold passing to respective inlets, each controlled by a knifegate valve. The lower ends of pairs of the pots pass material through respective outlet knifegate valves to respective first and second delivery lines. The respective knifegate valves and outlet knifegate valves of the pairs of pots are operable by respective common pneumatic actuators. Each pot has an ejector assembly having an upper chamber, an air injector nozzle, and an accelerator tube to create a venturi function. An air cycling valve transitions the upper chamber between a depressurized space and a pressurized space. The accelerator tube exhausts to a respective delivery line. Ejector assembly air is supplied via air control valve. The respective delivery lines each have an eductor port which allow for air to be ported into the line. The completed load and discharge cycle is governed by a pneumatic PLC and pneumatic timers. Output is scalable by operating the PLC to decommission a pair of pots or one of a pair of pots.
The scalability of output is attained at the penalty of having the footprint of 4 pots.